Strength of concrete depends upon amount of cement
content, quality and grading of aggregates, water of concrete ratio, compaction
and curing Strength of concrete increase very fast in the initial stage.
In the 7 days the strength gained is as much as 60 to 65
present of 25 days strength it is customary to assume the 28 days strength as
the full strength of concrete however concrete gains strength beyond 28 days
also.
The strength/grade of concrete is specified
and measured in newtons/sq. mm., meganewtons/sq. meter or even megapascals, in
fact the numerical figure will be the same in each case.
E.g. a strength of 20 newtons/sq.mm. is the
same as 20 meganewtons/sq.metre
Compressive strength of concrete
The characterize strength of
concrete is defined. As compressive strength of 150mm size cubes after 28 days.
Concrete mixtures can be designed to provide a wide range of mechanical and
durability properties to meet the design requirements of a structure. The
compressive strength of concrete is the most common performance measure
used by the engineer in designing building and other structures.
Tensile
Strength
The tensile strength of
concrete is usually considered about one-tenth of the compressive strength;
that is, concrete which has a compressive value of 2,000 pounds per square inch
should have a tensile strength of about 200 pounds per square inch. Although
there is no fixed relation between the two values, the general law of increase
in strength due to increasing the percentage of cement and the density, seems
to hold in both cases.
